"Bond funds" are terms used to describe a type of investment company (mutual fund, closed-end fund or unit investment trust (UIT)) that invests primarily in bonds or other types of debt securities. Depending on its investment objectives and policies, a bond fund may concentrate its investments in a particular type of bond or debt security - such as government bonds, municipal bonds, corporate bonds, convertible bonds, mortgage-backed securities, zero-coupon bonds—or a mixture of types. The securities that bond funds hold will vary in terms of risk, return, duration, volatility and other features.